Electron discharge devices



Nov. 11, 1958 B. H. SMITH 2,850,235

ELECTRON DISCHARGE DEVICES Filed Dec. 14. 1956 2 Sheets-Sheet 2 lNl/ENTORS BURTON 4 SMITH law 54 A T TORNEV United States Patent 6 ELECTRON DISCHARGE DEVICES Burton H. Smith, Belmont, Mass., assignor to Raytheon Manufacturing Company, Waltham, Mass, a corporation of Delaware Application December 14, 1956, Serial No. 628,303 '5 Claims. Cl. 315-39 This invention relates to a magnetron of simplified construction which may be manufactured at relatively small cost without sacrificing reliability of operation, and to an output coupling system incorporating said magnetron.

In the magnetron according to this invention, cost is reduced by minimizing the number of tube parts; this is achieved by transferring packaging parts from the tube to a separate unit whose cost is no greater than that of the packaging parts used in comparable tubes. This separate unit provides for supporting the tube, cooling the tube, making electrical connections to the tube, supplying the magnetic field and providing a suitable coupling between the magnetron and the transmission means to the load.

Radio frequency energy may be coupled from the anode resonator system by two electrically conductive cylinders that are connected to the anode so that they act as a dipole. This is achieved by connecting the upper cylinder to one set of alternate anode vanes and the lower cylinder to the other set of alternate anode vanes. Since alternate vanes are at opposite radio frequency potential in the normal mode of operation, the two cylinders are i at opposite radio frequency potential at any given instant and act as a dipole. through glass or ceramic bushings disposed at opposite ends of the magnetron and forming a part of the tube envelope.

The dipole radiator assembly has several advantages, one of which is that the anode is symmetrically loaded and produces a significant increase in the mode boundary over that which can be obtained in prior output systems wherein only one of the cavity resonators is loaded. Another advantage is that the cylindrical shields effectively shield the vitreous bushings from metallic vapors evaporating from the cathode and emanating therefrom in straight lines. These vapors condense on the inside of the electrically-conductive cylindrical shields instead of on the vitreous bushings, where the direct current input to the magnetron, as Well as the radio frequency energy radiated through the bushings, would be short-circuited. The vitreous bushings or domes, in addition to providing means for transferring radio frequency energy from with in the magnetron, provide heater-to-cathode insulation and insulation of the cathode from high voltage. The coupling can be varied readily by altering the diameter of the dipole cylinder in the region of contact with the magnetron anode. It has been found that a single cylinder, rather than two cylinders, may be used with satisfactory results. This cylinder is attached to alternate anode vanes only at either end of the anode structure.

The magnetron may be mounted within a waveguide or a cavity resonator, thus providing an output coupling arrangement for transferring energy from the magnetron to a utilization means. If a cavity resonator is employed, energy may be removed from the resonator by means of a coaxial output line. It has been found that by mounting the magnetron within a circular cavity resonator, a

These cylinders radiate energy ICE mode boundary superior to that with operation into a section of rectangular waveguide may be obtained.

Other objects and uses of the invention will become evident after reference to the accompanying description and drawings wherein:

Fig. 1 is a central cross-sectional view showing a mag netron in accordance with the invention;

Fig. 2 is a pictorial View of one of the dome assemblies used in the magnetron shown in Fig. 1;

Fig. 3 is a view showing the magnetron anode assemy;

Fig. 4 is a View of the other dome assembly used in the magnetron of Fig. 1;

Fig. 5 is a view showing a portion of the anode assembly using a single strap shield and indicating an alternative method of connecting the cylinder on strap shield to the anode;

Fig. 6 is the pictorial view showing the tube of Fig. l mounted within a waveguide and showing the external magnetic field-producing means;

Fig. 7 is a detail view showing a portion of the tube mounting means of Fig. 6; and

Fig. 8 is a pictorial view, partially in section, showing the tube of Fig. I mounted within a cavity resonator.

Referring to Figs. 1 to 7 of the drawing, wherein corresponding elements are designated by the same reference numeral, the magnetron 10 consists essentially of a centrally disposed cathode assembly 50, and a surrounding anode assembly 12 situated between two dome assemblies 30 and 40 which are transparent to radio frequency energy generated by the magnetron, and a transverse mag netic field-producing means 80, shown in Fig. 6.

The anode assembly 12 includes an anode cylinder 13 from whose inner periphery radially extend several anode vanes 14, soldered or otherwise secured to the: anode cylinder. Alternate anode vanes may be interconnected in the usual manner bypairs of concentric straps 15, 17, one pair located at each end of the anode block. The first pair 15 of straps is set in slot 16 in the anode vanes 14 and the second pair 17 of straps is positioned in slots 18 in the anode vanes. The invention, however, is not limited to a strapped magnetron.

A first annular electrically conductive strap shield or cylinder 21 is electrically and mechanically connected to alternate anode vanes 14; strap shield 21 contains slots 22, shown in Fig. 3, along one edge at positions adjacent alternate anode vanes whereby the strap shield 21 is C011: nected electrically to alternate vanes only. The vanes not connected to strap shield 21 may be provided with slots 23 in alignment with the strap shield, as indicated in Fig. 5. A second annular strap shield or cylinder 24 is disposed on the opposite side of the anode vanes from strap shield 21, as shown in Figs. 1 and 3, and is connected to alternate anode vanes lying between the alternate vanes to which a first strap shield 21 is connected. It is possible to connect both strap shields to the same side of the anode block.

A pair of end cooling fins 26 and 27 and a central cool,- ing fin 28 are soldered to the outer periphery of anode cylinder 13. The central cooling fin 28 is provided with a discontinuity to permit passage of an exhaust stem 29,, one end of which passes through an aperture in anode cylinder 13. i

A dome assembly 30 includes a glass bushing 31, and an annular bushing disk 32 and a bushing adapter 33, said bushing disk and bushing adapter being made of a material, such as Kovar, having approximately the same coefficient of thermal expansion as that of glass bushing 31. Dome assembly 30 further includes a pole sleeve 34 and a pole piece 35 apertured to receive a cathode tube 51 to be referred to subsequently. The glass bushing 31 -is hermetically sealed both to the bushing disk 32 and the an extension of anode cylinder 13: The strapshields serve not only asradiating coupling means, but'also-to shield I the glass bushings from the cathode so that metals emitted from the cathode-cannotdeposit on the glass bushing.

A second dome assembly;40;" similar to-that previously described, is mounted on--the-other side of 'theanodeassembly -12 andincludes a glass. bushing 41, bushing disk 42, bushing adapter 43, pole sleeve 44 and pole piece 45.-

The glass bushing --41 is sealedtobushing disk 4.2 which, in turn, is in contact with one flat surface of anode cylinder 30=oppositethattowhich the bushing disk 32 of dome assembly 30 is attached. Dome assembly .40. isvhermetically sealed to the anode assembly 12"by welding, as at 46, the edge of bushing disk 42 to the end cooling fin. 27, which forms an extension of the'anode cylinder.

The cathode assembly 50 comprises a cathode tube 51 surrounded at the central portion thereof by awire mesh 52 containing an electron-emissivematerial; wire mesh, for example, may have metal, powder brushed into the mesh'and may be sintered to the cathode tube. A heater wire 53 is contained within cathode tube 51; one end of,

heaterwire 53 is attached, as by a spot welding, to the inner periphery of cathode, tube 51 at one end, as shown in Fig. 1. The cathode tube 51 also is-secured to the pole piece 35 of dome assembly 30, a by Welding. An end cap 55 is hermetically'sealed to the pole sleeve 34 as by weld. 56. The other ;end of the heater wire-53is fastened to a connector wire 57 which, in turn, is secured at more than one point to an end cap 58; This modevof attachment is superior mechanically to the direct attachment of the heater wire to end cap 58, although/either; type of connection is withinthescope of this invention.

End cap 58 is sealed hermetically to the pole, sleeve 44,.as

by the weld 59. It should be noted that the cathode tube.

51 is electrically isolated from pole piece 45.

The magnetron 10,-which includes anode assembly 12,.

dome-assemblies 30 and 40,,and cathode assembly 50, is mounted within a waveguide generally designated by reference numeral 60. The mounting means 65 for magnetron 10, which includes a cathode connector66, consists of a flat portion 66a terminating at one end in a flanged portion 66b, and a tubular member 67 projecting from the fiat portion 66a, as shown in Fig. 7. The inner periphery 68 of the member 67 is .adapted to surround the pole sleeve 34 of dome assembly 30 of Fig. 1, while the tapered outer periphery 69 engages the tapered outer surface of the bushing adapter 33, shown in Fig. 1. The flanged portion 66b is attached to the wave guide by appropriate fastening devices 71.

The tube mounting means 65-further includes a heater connector '78 having a flat portion 78a and a flanged portion 78b, similar to the cathode connector 66, except that the projecting member 73 is cylindrical and is adapted to fit against the outer periphery of the pole sleeve 44 of dome assembly 4-0, shown in Fig. 1.

A connecting clip 75 fits over an opening in thenarrow wall 61. of waveguide 60 through which external circuit leads may pass. Clip 75 includes portions 76 which fit against the broad walls of the waveguide and bent portions 77, which assist in maintaining the clip in position against the Waveguide. A ground (cathode) terminal 90, heater terminal 91 and high voltage (anode) terminal 92 provide electrical connec tionsto the cathode 50, heater 53, and anode 12, respectively; these terminals are insulated from the waveguide 60 or other tube elements, as the case may be, by means of electrically insulated bushings 94. The

cathodeyconnector 66 may be connected directly to the waveguide .wal 1, by means of t he fastening devices 71 in applications where the cathode is maintained at ground potential: If the cathode is to be heldat a potential other" than ground, the cathode member 66, of course, would be insulated from the waveguide Wall, in a manner to be shown in connection with the heater connector 78, and the terminal 91 would be connected to an appropriate negative terminal of a heater supplyr,

The heater connector 78, whose flat portion 78a is spaced from thebroad 'wallof thewaveguide, is electrically insulated from the narrow wall of waveguide 60 and from' magnetto the waveguide transition unit 60. The polepieces of the magnet 80 are axially aligned with the inter-- action space between the cathode 50 and the tips of anode vanes 14. As previously stated, the pole piece 35, to which cathode 50 is connected, may be operated at ground potential, in which event the ground terminal of the heater voltagesource (not shown) is connected by way of the cathode terminal to the pole piece 35. The other heater supply terminal is .then connected by way of the heater terminal 91 totheotherpole piece 45 of. magnetron 10;. The. high voltage sourceis connected between the anode: and ground. Radio.frequencyenergy may be extracted." from the...open end .of the waveguide, which is adapted; to be connected to any desired load, in a well-known.

manner.

A modificationof the invention'as shown in Fig. 6 isv shown in.Fig..8 in which;the transition unit comprises a cyclindrical cavity resonator anda coaxial line 102, rather thanthewaveguide 60-of Fig. 6. In this embodi- I ment, thetube radiates radio frequency energy intothe.

cavity resonator 100 and the energy within the latter ,is supplied to an external load by means of a coaxial line 102 coupled to theresonator. A stub 103 is provided for= coupling adjustments and may be preset for a given tube.

The coaxial line 102 may be supported from the outer surface of the resonator 100 by the bracket 104. The. remainder of the assembly of Fig. 8 is similar to that.

shown in Fig. 6, except, of course, for theshape of the mounting brackets 75.

This-invention is not limited to the particular details or construction materials and processes described, as many equivalents will suggestthemselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is; 1. In combination, an electron discharge devlce comprising an evacuated envelope having a portion thereof transparent to electromagnetic energy and containing therein an anode assembly including a plurality of spaced members, a cathode arranged adjacent said anode members, means for producing a magnetic field transverse to the region betweenthe cathode and the anode assembly, means for radiating energy generated within said electron discharge device through said portion of said envelope, said means for radiating including a cylindrical electricallyconductive member connected to a set of alternate anode members, an energy containing means, means for mounting said discharge device within said energy containing means, a pair of magnetic pole pieces each fixedly at tached to said portion of the envelope at a corresponding 2. In combination, an electron discharge device comprising an evacuated envelope having a portion thereof transparent to electromagnetic energy and containing therein an electrode capable of propagating high frequency energy, a cathode, a heater, a magnetic fieldproducing means having oppositely disposed pole pieces, means including said magnetic field-producing means for directing said electrons in paths adjacent said electrode, means for radiating energy generated within said electron discharge device through said portion of said envelope, said means for radiating including a cylindrical electrical conductive member connected to spaced portions of said electrode, said cathode being connected to one pole piece of said magnetic field-producing means, said heater being connected to the other pole piece of said magnetic field-producing means.

3. In combination, an electron discharge device comprising an evacuated envelope containing therein an anode assembly including a plurality of spaced members, said anode assembly being connected to a first portion of said envelope, a cathode arranged adjacent said anode members, means including a pair of oppositely disposed magnetic pole piece assemblies for producing a magnetic field transverse to the region between said cathode and said anode assembly, said envelope having electrically insulating portions intermediate said first portion and a corresponding one of said pole piece assemblies which is transparent to electromagnetic wave energy, and means for radiating energy generated within said electron discharge device through said electrically insulating portions of said envelope, said means for radiating including a first cylindrical electrically-conductive member connected to one set of alternate anode members, and a second cylindrical electrically-conductive member connected to the other set of alternate anode members.

4. In combination, an electron discharge device comprising an evacuated envelope having a portion thereof transparent to electromagnetic energy and containing therein an anode assembly including a plurality of spaced 6 members, a cathode arranged adjacent said anode members, means for producing a magnetic field transverse to the region between the cathode and the anode assembly, means for radiating energy generated within said electron discharge device through said portion of said envelope, said means for radiating including a cylindrical electrically-conductive member connected to a set of alter nate anode members, a pair of magnetic pole pieces each attached to said portion of said envelope at a corresponding end of said device, a waveguide, and means for mounting said device within said waveguide, said mounting means including means connected to a corresponding pole piece and supported from said. waveguide.

5. In combination, an electron discharge device comprising an evacuated envelope having a portion thereof transparent to electromagnetic energy and containing therein an anode assembly including a plurality of spaced members, a cathode arranged adjacent said anode members, means for producing a magnetic field transverse to the region between the cathode and the anode assembly, means for radiating energy generated within said electron discharge device through said portion of said envelope, said means for radiating including a cylindrical electrically-conductive member connected to a set of alternate anode members, a pair of magnetic pole pieces each attached to said portion of said envelope at a corresponding end of said device, a cavity resonator of cylindrical configuration, and means for mounting said device Within said cavity resonator, said mounting means including means connected to a corresponding pole piece and supported from said cavity resonator.

References Cited in the file of this patent UNITED STATES PATENTS 2,478,534 Kather Aug. 9, 1949 2,542,899 Brown Feb. 20, 1951 2,680,827 Randall et al. June 8, 1954 

